The present invention is directed in general to communication systems for vehicles and more specifically to a method an apparatus for optimizing file transfers between a vehicle and a remote site, e.g., a remote monitoring and diagnostic service center.
Establishing, maintaining and managing a communications link between a mobile asset (e.g., an on-road, off-road or rail-based vehicle) can provide opportunities for cost-saving operation through efficient vehicle dispatching and the remote acquisition of vehicle performance information. When the mobile assets comprise a fleet of similar vehicles, economies of scale can result in considerable savings and operational efficiencies. As applied to railroad operations, cost-efficiency requires minimization of locomotive down time and especially the avoidance of line-of-road locomotive failures. Failure of a major locomotive system can cause serious damage, require costly repairs, and introduce significant operational delays in the railroad transportation network. A line-of-road failure is an especially costly event as it requires dispatching a replacement locomotive to pull the train consist, possibly rendering a track segment unusable until the disabled train is moved. As a result, the health of the locomotive engine and other locomotive subsystems is of significant concern to the railroad operator.
In the past, there has been no automatic or systematic mechanism for locomotive fault detection. Instead, the railroad operator relies primarily on regular inspections and the observation of performance anomalies by the locomotive operator. Also, some cursory inspection processes are accomplished while the locomotive is in service. More thorough inspections require the locomotive to be taken out of service for several days. Any locomotive down time, whether for inspection or repair, represents a significant railroad cost that advantageously should be minimized. The same inspection procedures are generally applied to off-road, on-road, and other rail-based vehicles.
One such apparatus for detecting faults, and thereby minimizing locomotive down time, is an on-board monitor that measures performance and fault-related operational parameters of the mobile asset during operation. With timely and nearly continuous access to vehicle performance data, it is possible for repair experts to predict and/or prevent untimely failures. Through the off-board analysis of this information, timely indications of actual and expected component failures can be derived. Also, repair recommendations can be generated to correct failures or avoid incipient problems.
The on-board monitor collects, aggregates and communicates vehicle performance and fault related data from an operating vehicle to a remote site, for example, a remote monitoring and diagnostic center. The data may be collected periodically, when various anomalous or triggering events occur during vehicle operation, or when the vehicle experiences a failure. Generally, the anomalous data and the fault data are brought to the attention of the vehicle operator directly by the vehicle systems, but the vehicle itself lacks the necessary hardware and software devices to diagnose the fault. It is therefore, advantageous to utilize the on-board monitor to collect and aggregate the information and at the appropriate time, send the information to a remote site, for example, a monitoring and diagnostic service center. Upon receipt of the performance data at the monitoring and diagnostic service center, computer based data analysis tools analyze the data to identify the root cause of potential or actual faults. Also, experts in vehicle maintenance and operation analyze the received data to prepare recommendations for preventive maintenance or to correct existing faults or anomalous conditions.
Historical anomalous data patterns or fault occurrences can be important clues to an accurate diagnosis and repair recommendation. The lessons learned from failure modes in a single vehicle can be applied to similar vehicles in the fleet so that the necessary preventive maintenance can be performed before a line-of-service breakdown occurs. When the data analysis identifies incipient problems, certain performance aspects of the vehicle can be derated to avoid further system degradation and further limit violations of operational threshold until the vehicle can undergo repairs at a repair facility.
The on-board monitor aboard the off-road, on-road or rail-based vehicle monitors and collects data indicative of vehicle operation from several vehicle control systems. The on-board monitor interfaces with a communications for transmitting the data collected to the remote site for analysis. When the on-board monitor and its attendant communications system is first installed on board a vehicle, a commissioning process must be executed so that the unique vehicle identification is associated with the unique communications access number or identifier for the communications system on board the vehicle. Whenever information is received at the remote site it is tagged with the communications access number or identifier of the communications system from which it was sent. To properly link the performance information to the correct vehicle, a cross reference table is consulted. Using the communications system number as an index into the table, the unique vehicle identification number associated with the transmitting communications system number is obtained.
Once commissioned, the communications system can establish a link between the operating vehicle and a remote site to transmit fault, anomalous and operational parametric and location information from the vehicle to the remote site. Further, control information and instructions can be uploaded from the remote site to the operating vehicle.
The remote site and the operating vehicle also exchange configuration information. For example, the remote site sends a configuration file to the vehicle to identify the parametric information to be collected and the frequency with which that information is to be collected. Configuration information sent to the operating vehicle also includes identification of certain anomalous or fault events and thresholds used to declare the occurrence of such events. Finally, the configuration process includes a sub-process wherein the version of software programs running on the vehicle are compared with the software version that should be executing on the vehicle, which information is stored at the remote site. To accurately assess the condition of the vehicle based on the downloaded data, the remote site must know the software version running on the vehicle. When a vehicle fails in operation, it is crucial that the parametric operation information collected by the on-board monitor be transmitted as soon as possible to the remote site. If the remote site is a monitoring and diagnostic service center, analysis can immediately be undertaken on the received data for determining the cause of the fault and possibly for suggesting derating of certain operational features to prevent further damage to the vehicle. Further, in one embodiment, the on-board monitor includes a device for determining vehicle location, for example, a global positioning system receiver. In this embodiment, location information can also be provided to the remote site so that a repair crew can be dispatched to the vehicle.
The process of providing the vehicle operational information to a remote site, e.g., a monitoring and diagnostic service center, requires the creating of a communications link between the two points. This link can be established using satellite communications or terrestrial communications, including cellular, personal communications, microwave, etc. As applied to an embodiment where the on-board monitor is on a locomotive, typically satellite communications is utilized since the locomotive may frequently be outside the range of available terrestrial communications systems. In one embodiment, transmission control protocol/internet protocol (TCP/IP) is utilized on the communications channel.
Whether the link comprises satellite communications or terrestrial communications, delays are encountered in the transmission process. The first delay is simply the time required to close the communications link from the vehicle to the remote site (or in reverse, for transmissions from the remote site to the vehicle). A second delay element is introduced by the transit time, i.e., the time interval between transmitting the first bit from the vehicle and receiving the first bit at the remote site. There is also a latency delay between individual files as each file is taken from the queue and prepared for transmission. The total latency is a function of the number of files to be transmitted. When a vehicle experiences a fault, it is important to transfer all operational parametric information to the remote site so that a complete and thorough diagnosis can be undertaken there. Therefore, transmission of a significant number of files may be required when a fault occurs, creating significant total latency due to the latency period between each transmitted file. Also, errors during transmission require retransmission of the file and thus add to the delay. Even in those situations where forward error correction is employed, performing the forward error correction on the received data consumes a certain amount of time. Finally, all communications links are prone to failure, i.e., the link simply goes down or the bit error rate or signal strength renders the link unusable. Also, in the embodiment where the vehicle is a locomotive, the links is lost whenever locomotive enters a tunnel. As is known, wireless environments pose more challenges with respect to links outages than wired environments.
It must also be recognized that the file that was being transmitted when the link was lost, must be completely retransmitted again. The data in the file is worthless until the last file bit arrives at its destination. All of these factors contribute to transmission delays and according to the teachings of the present invention are minimized to allow the early receipt of information at the remote site so that data analysis can begin at the earliest possible time.
The method and apparatus in conjunction with the present invention categorizes the various types of data to be downloaded from the vehicle to the remote site and further identifies an appropriate downloading strategy. Certain relatively high priority files (e.g., related to serous faults or emergency conditions) are downloaded prior to downloading lower priority files. In this way, data analysis at the receiving site begins immediately after the high priority files are downloaded, thereby saving processing time that would otherwise require the downloading of the low priority files before processing the received information. Further, the number of files is reduced to reduce network latency, especially the network latency that arises between each file, by merging similar files. But the file lengths are not permitted to become so long so as to create problems if the link is lost during transmission of the file. To reduce network latency to its lowest possible value, all files can be combined into one super file. However, when the link is lost the entire file must be retransmitted. Therefore, the process of selectively combining related files results in the optimum file transfer characteristics.